Reciprocating roller chain drive systems have many applications and have been used on numerous mechanical systems. Briefly, a sprocket transfers driving force from a motor, or other source of power to a roller chain which transfers the driving force to a mechanical apparatus such as a carriage, trolley, shaft, wheel, gear box, or the like, which is to be driven.
For example, a carriage assembly may be series connected into the roller chain path, wherein the driving force is used to move the carriage assembly along a track, or to follow the path of the reciprocating roller chain. In this case, the second sprocket (idler or driven sprocket) is used to complete the roller chain path and may transfer the driving force to a mechanical apparatus. As can readily be seen, numerous manufacturing, production and operating applications may use a reciprocating roller chain, for example, to move components from one point to another for assembly or to provide reciprocating rotational power to a shaft, a gear box, or the like.
Providing a protection device in the roller chain path is highly desired, particularly when the roller chain is tensionally stronger than the carriage assembly or mechanical equipment which is to be driven by the reciprocating roller chain. This is particularly true when the carriage assembly or mechanical equipment is more expensive than a roller chain, and the time required for replacement would be much greater than replacing or reinstalling a roller chain.
A protection device is desirable which will open the driving path of the roller chain and will prevent excessive force from being applied to the carriage assembly or mechanical equipment when the driving force exceeds the strength which can be withstood by the carriage assembly, or mechanical equipment, but is less than the tensional strength of the roller chain. Thus, by opening the driving path of the roller chain, possible damage to the carriage assembly or mechanical equipment is prevented.
A tension link control device is disclosed by U.S. Pat. No. 3,922,104 to McCullough, which includes an inner and outer cylinder with a fracture link therebetween. This fracture link will separate as tensional force is applied. Further, the fracture link is specially configured with threaded ends and is held within a semi-circular bored member using the threaded ends and set screws. The McCullough tension link control device contains several drawbacks, among them is the large number of steps required to assemble the tension link control device both initially, and to replace the fracture link once separation occurs. Moreover, a high degree of precision is required to manufacture the McCullough link control device. The fracture link is made with chemically analyzed steel and must be calibrated to achieve a high order of surface smoothness. The fracture link is held in place using threads which must have a special thread pitch with a considerable amount of axial play (this play must be on the order of approximately 0.07 inches). Further, the actual thread play must be computed for each application of the tension link control device as based upon thread profile, thread pitch, material shear strength and design of fracture loads.
In view of the foregoing disadvantages and drawbacks due in part to the high degree of precision required to manufacture and install the tension link control device, a mechanical protection device (mechanical fuse), such as the present invention, which will protect more expensive components of a mechanical system used with a reciprocating roller chain is highly desirable. The present invention provides a mechanical fuse which is less complicated, more easily installed and easier to manufacture and replace when compared with the prior art.